The Effect of ozonation on municipal sludge reduction(optimization of sludge reduction by ozone dosage, pH changesand retention time)

Sewage sludge production especially in Activated sludge process is currently considered as one of the most important problems in wastewater treatment due to the high costs of management and treatment, as well as limitations in its reuse. According to the importance of the subject in waste sludge management which standson the 3Rs’ (reduce, reuse and recycle), numerous studies addressing this need to minimize the sewage sludge production have been done.The significant drawbacks of activated sludge process is the production of biological excess sludge and its treatment and disposal of are evident in most parts of the world, namely ourcountry. A suitable solution for this problem would bedecreasing the excess sludge via decreasing the yield coefficient.In this study, four reactors are used and effective parameters such as COD, MLSS, TSS, pH, and Y coefficient are measured.Different concentrations of ozone in were used to oxidize part of the ludge. The results showed that the 24 mg ozone per gram of MLSS in one liter of the returned sludge to the reactor in 10 days as retention time will lead to reduction of Yield coefficient from 0.65 to 5.33 CODmgBiomassmg. In other words,reduction of excess sludge up to 85%.In the next stage of this study, the pH range was shifted from neutral to acidity and alkalinity, and at pH=3 sludge reduction was equal to 4.18 CODmgBiomassmg. It means the sludge reduction is almost 100%.